Cap



1944. cosTA ETAL ,33

CAP

' Filed NOV. 7, 1941 3 Jc'omz, 3,

Edward Y I cl'qr 09,33,072.

Patented Jan. 11, 1944 Md., assignors to Crown Cork & Seal Company,Inc., Baltimore, Md., a corporation of New York Application November7,1941, Serial No. 418,248

2 Claims.

The present invention relates to container closures, and particularlyclosures of the crown type which include a metal shell having a crimpedor corrugated skirt and a cushion sealing liner or disc' assembledwithin the shell. The closure or cap is applied to a container such as astandard crown beverage bottle by drawing the crimped skirt into lockingengagement with a shoulder on the container lip whereby the liner istightly compressed thereon to seal the contents against leakage past thelip surface. This crowning pressure frequently reaches as high as 900pounds and it is necessary for the cushion liner to have a high degreeof permanent resiliency under this pressure so as to constantly flow andfill any inequalities in the lip surface and maincork granules heldtogether by a binder such as lue or synthetic resin, the cork beinglargely predominant and the 'binder'being present substantially only inan amount to hold the cork granules together. Such cork liners or discsare generally cut so as to have a total thickness of about 0.1 inch andunder crown sealing compression are reduced to a thickness of the orderof 0.017 inch. Notwithstanding such high degree of sealing compression,the cork composition disc maintains its permanent resiliency and scalingproperties as evidenced by the tightness of the seal and further by itsrapid expansion or return when the compression is released after longperiods of time. In addition, the cork composition liner does not shrinkto any appreciable'extent, and withstands high internal pressures of 120pounds or more such as are created by carbonated beverages, e. g., beer,so that a leakproof seal is continuously maintained and the contents arprevented from seeping or exhausting between the liner and the lipsurface Of the container. It can be appreciated from the foregoing whycrown caps including a cork sealing liner have been preferred. However,at, th present time, due'to remote sources of supply and to nationaldefense needs, sufiicient cork to meet the requirements of the closureindustry is no longer assured.

To improve this situation, experiments have been conducted withnewsboard, "wood-pulpboard, straw board, "sulphit board, press board andvulcanized fiber board, all of which are commercially available and havebeen adequate in th case of screw or lug caps where a high sealingcompression comparable to that occasioned by crown scaling is notencountered. These inexpensive board materials and many othersnotwithstanding they have been faced with foil, paper or resistantcoatings have not made satisfactory crown caps for sealing. pressurebeverages and liquid." because the sealing liner lacks the requiredpermanent resiliency under high sealing compression, tends to shrinkobjectionably and is not resistant to leakage under internal pressuresproduced by carbonated beverages.

We have discovered that a crown cap having a cushion liner of paperboard is equally as suitable as a cap provided with a cork cushionliner, provided the liner .hasincorporated therein in addition to boardpulp, raw chemically untreated, i. e., uncooked, fibers such as cottonfibers, in amount effective to produce relatively permanent orcontinuing resiliency under high sealins compression. It is preferredthat the board .pulp to which is added the raw fibers be mostlymechanical pulp, i. e., contain littl or no cooked fibers. These latterapparently so deaden the liner that it remain substantially set undercompression and is not as readily improved by theinclusion of theuntreated fibers as those pulps which contain no treated fibers or asmall proportion of the same. Uncooked non-ligneous fibers are preferredas the resiliency imparting agent for all types of board pulps.

The primary object of the invention is to provide a closure cap of thecrown type having a cushion liner made of paper board which will possessthe required permanent resiliency under high sealing compression to forma leakproof' when subjected to crowning pressures, the thick ness isreduced to substantially 0.017 inch to 0.028 inch and under crownsealing compression, the liners exhibit substantially the samecontinuing resiliency, resistance to internal pressures and lack ofshrinkage, as well as sharp rebound on release of pressure whichcharacterize composition cork liners under the same conditions.

An equally important object of the invention is to provide a closure capof the crown type having a cushion liner which can be made by high speedproduction methods and at a cost comparable to the use of corkcomposition.

In the accompanying drawing, we haveillustrated a crown cap for astandard crown beverage bottle and it is to be understood that othertypes of closure caps are similarly improved by use of the presentinvention.

Referring to the drawing:

Figure 1 is an elevation of the inside of a crown cap showing thecushion liner assembled therein;

and

Figure 2 is a section on theline 2-2 of Figure 1.

The cap shown in Figure 1 includes a metal shell l having a skirt H, asshown in Figure 2, and formed with crimps or corrugations I2. In thecase of a standard crown beverage bottle, such caps are usuallydescribed as standard 26 mm. crown which means that the diameter takenfrom the inside perpendicular wall of the skirt l I is 26.7818 mm: or1.0545 inches. The invention is equally satisfactory with other types ofcrowns of both larger and smaller diameters. The cushion liner is in theform of a circular disc l3 and is assembled in the shell and securedthereto in any suitable manner.

In Figure 2, the cushion liner is shown having its uncompressed ororiginal total thickness. The

- exposed surface of the cushion liner I3 has adhered thereto a' spotfacing I4 of paper, foil or in the form of a suitable coating ofresistant material such as vinyl resin or chlorinated rubber. Thisfacing l4,'in some cases, extends over the entire exposed surface of theliner so as to give overall coverage.

In preparing the material from which the liners are formed, a suitablepaper pulp is employed, preferably mechanical pulp or one containingmostly untreated fibers as explained above. merous board pulps are, ofcourse, available from which a boardhaving improved sealing qualitiescan be made by the inclusion therein of an effective amount of uncookedfibers, such as cotton fibers, to impart the desired compressibility andresiliency. For example, a mechanical pulp such as that prepared fromseasoned ground wood is highly satisfactory although not available atthe present time in required quantities. .Likewise,

Waste news'containing mostly uncooked fibers and about 15% of sulphitepulp, forms a very suitable board, although not now obtainable incommercially useful amounts. Ground wood made from green wood and havingincluded about 15% sulphite pulp is the most suitable pulp avail ableunder current circumstances since it can.

be obtained in sufficient amount and at a commercially acceptable price.These respective pulps make satisfactory boards forcushion linersticularly compatability with the raw, live, un-

cooked fibers which are added in effective amount to make the boardpermanently resilient.

With a pulp of the character just described, there is mixed raw,uncooked fibers in amount to produce in the finished board,compressibility and rebound of the order of the characteristiccontinuing resilience of composition cork. That is, crown liners cut outfrom the board will exhibit relatively permanent or continuingresiliency under high crown Sealing compression and form a reliableleakproof seal between the-crown cap shell and the lip of a containerfor an indefinite period.

Experiments were made using sulphite pulp, sulphate '(kraft) pulp, sodapulp, straw pulp, rag pulp, and cotton linters pulp as the resiliencyimparting agent; but .in each case, the resulting board did not possesssealing qualities of the order of composition cork when used for crowncushion liners. On the other hand, raw, untreated fibers, preferablyvegetable fibers and non.- li'gneo'us fibers, such as cotton floss,cotton linters, and ginned cotton, were'found to be satisfactory andenhanced the resilience and strength of the cushion liner material sothat it was substantially as satisfactory under high crown sealingcompression as composition cork. While we have referred to cotton fibersas the resiliency imparting agent, it will be appreciated that otherfibers are equally suitable, such as flax, ramie,

nection with the use of 25% cotton floss, 63.75%

green ground wood and 11.25% sulphite pulp. The invention is equallyoperative with the other pulps and fibers referred to and We do not wishto be limited to the specific proportions in the example just recited.With respect to the 'relative percentage of pulp and raw fibersresiliency-imparting, the compressibility and rebound, i. e.,resiliency, increases as the amount of cotton fiber, which in thepresent example is cotton floss,

is increased from 15% to 25%. At about 25%, the maximum resilienceappears to be obtained. With further additions of such raw fibers theresilience tends to decrease, and when the product contains 63% of rawfibers, the compressibility and rebound is about the same as that of thepulp without the fiber addition. It will be seen that the proportions ofraw fibers to pulp are critical to assure maximum resiliency for anunlimited or indefinite period of time. In some cases, the pulps willhave a compressibility and rebound characteristic so that less than 25%of live fiber may be included to give a satisfactory result, and inother cases there are pulps which are so lacking in the compressibilitand rebound factor that somewhat more than 25% may be necessary to bringthe final material to the required permanent resiliency.

In preparing the pulp mixture for the paper making operation, the cottonfibers are first speed of hydration. For example, cotton linters,

since they are short fibers, need not be given a preliminary beating asis done in the case of cotton floss. When the beaten stock is fed to thepaper machine, the pulp dilution should be controlled so that the driedboard product will have the desired thickness, density and resilience.The two factors of hydration of the pulp and dilution are critical tothe end that when the cushion liner is subjected to high sealingcompression, it will exhibit permanent resilience, and not become deador so lose its compressibility and rebound characteristic as to produce.leakers. At this tween 0.031" and 0.056".

point, it should be understood that liners made in accordance with thisinvention may be stored for long periods before and after assembly incaps and as pointed out, will hold a seal indefinitely.

-The stock -is fabricated on acylinder paper making machinepreferablyhaving six cylinders although satisfactory boards may be madeusing as little as three or as many as seven or more cylinders. Stockdilution is generally increased when a greater number of cylinders areused and correspondingly decreased when a fewer number ofcylinders isemployed.

The board produced on the cylinder machine is dried by the usual dryingmeans which finish the materialawith a moisture content of between 2/z%and 8%. We prefer to calender the product lightly to render the surfacessmooth and suitable to receive the facing H, the reduction in thicknessdue to calendering being controlled so that it is not more thansubstantially 15% and is preferably held at about 10%.

The board material may have adhered to one or both surfaces thereof afacing ll of one or;

two sides coated varnish paper, metal foil, such as aluminum foil, or aresistant material, such as vinyl resin or chlorinated rubber, and thediscs are then punchedirom such laminated product. The discs areassembled in the caps with the facings exposed to the contents. In lieuof punching out such laminated cushion liners, the

liners may be punched from the board and subsequently provided with aspot or overall facing of one of the materials above mentioned. Also,-acoating may be suitably sprayed on the surfaces of the board and thediscsthen punched out.

For example, a coating composed of a mixture of latex, casein, andinorganic filler, may be cylinder machine roduct.

vthe severe pressures entailed in the crowning operation and the crownsealing compression, the residual thickness will be between 0.017" and0.028". and at the same time, the cushion liner will retain itsresilient properties for an indefinite period of time, as ischaracteristic of the usual cork composition liner. By the presentinvention, a product is obtained which, under the most severe sealingpressures, has a residual thickness within the range of thatcharacteristic of the customary cork disc, and like the cork disc atthis residual thickness has sufficient compressibility and rebound toafford a permanent leakproof seal. Products made in accordance with thisinvention, after drying or after drying and light calendering, andbefore facing, preferably have an original or total thickness of be- Theoriginal or total thickness is critical only to the extent that underthe high pressures above mentioned incident to the-crowning operationand the crown sealingcompreSsio'n, the cushion liner will be reduced toa residual thickness described which is of the order of that to, whichcork composition is reduced under similar conditions, and at the sametime retain the continuing resilience and other sealing qualitiescharacteristic of the customary cork disc.

The term crowning pressure is intended to denote the pressure exerted bythe crowning apparatus in looking the crimped skirt of a crowned capupon the locking shoulder of a container such.

this. pressure is in the neighborhood of 900 pounds and constitutes ahigh sealing pressure, l. e., the crowning pressure is substantially thesame as the continuing sealing pressure.

The term resiliency is intended to cover the properties of highcompressibility and quick rebound when the compressing force isreleased, which properties are possessed substantially alike by theliner disc described herein and the heretofore used cork compositiondisc. these properties, the cushion liner at all times closes anyopenings or fills any inequalities between tainer.

-We claim:

1. A crown cap having a the cap and the sealing lip of the concushionliner of paper board, said board comprising ligneous untreatedmechanical paper fibers in major amount, and in lesser amount, rawchemically untreated nonligneous vegetable fibers, said cushion linerhaving a thickness of substantially .031" to .056" and said untreatednon-ligneous fibers being present in amount to impart to the liner aresiliency of the order of cork composition cap liners. v I

2. A crown cap having a'cushion liner of paper board, said boardcomprising ligneousuntreated mechanical paper fibers in major amount,and in lesser amount, raw chemically untreated nonligneous vegetablefibers, said cushion liner having a thickness of substantially .031" to.056" and said untreated non-ligneous fibers being present in amount ofsubstantially 15 to 25%. EDWARD'J. COSTA.

VICTOR A. RYAN.

It is a critical requirement of discs produced Because of

